Update {virtual,override} to follow C++11 style in components.

components/dom_distiller/core/dom_distiller_test_util.h

Index: components/dom_distiller/core/dom_distiller_test_util.h
diff --git a/components/dom_distiller/core/dom_distiller_test_util.h b/components/dom_distiller/core/dom_distiller_test_util.h
index 3b7ecd4198416edc7d9ab13cf3cd129edd62561b..8d22a256024f8e1023fdb3132cf7641794daa22c 100644
--- a/components/dom_distiller/core/dom_distiller_test_util.h
+++ b/components/dom_distiller/core/dom_distiller_test_util.h
@@ -26,11 +26,11 @@ class ObserverUpdatesMatcher
       const std::vector<DomDistillerObserver::ArticleUpdate>&);
 
   // MatcherInterface overrides.
-  virtual bool MatchAndExplain(
+  bool MatchAndExplain(
       const std::vector<DomDistillerObserver::ArticleUpdate>& actual_updates,
       testing::MatchResultListener* listener) const override;
-  virtual void DescribeTo(std::ostream* os) const override;
-  virtual void DescribeNegationTo(std::ostream* os) const override;
+  void DescribeTo(std::ostream* os) const override;
+  void DescribeNegationTo(std::ostream* os) const override;
 
  private:
   void DescribeUpdates(std::ostream* os) const;